Kinetic study of copper(I)-catalyzed click chemistry step-growth polymerization

Oligomers and polymers containing triazole units were synthesized by the copper(I)-catalyzed 1,3-dipolar cycloaddition step-growth polymerization of four difunctional azides and alkynes. In a first part, monofunctional benzyl azide was used as a chain terminator for the polyaddition of 1,6-diazidohexane and alpha,omega-bis(O-propargyl)diethylene glycol, leading to polytriazole oligomers of controlled average degree of polymerization (DPn = 3-20), to perform kinetic studies on low-viscosity compounds. The monitoring of the step-growth click polymerization by H-1 NMR at 25, 45, and 60 degrees C allowed the determination of the activation energy of this click chemistry promoted polyaddition process, that is, E-a = 45 +/- 5 kJ/mol. The influence of the catalyst content (0.1-5 mol % of Cu(PPh3)(3)Br according to azide or alkyne functionalities) was also examined for polymerization kinetics performed at 60 degrees C. In a second part, four high molar mass polytriazoles were synthesized from stoichiometric combinations of diazide and dialkyne monomers above with p-xylylene diazide and alpha,omega-bis(O-propargyl)bisphenol A. The resulting polymers were characterized by DSC, TGA, SEC, and H-1 NMR. Solubility and thermal properties of the resulting polytriazoles were discussed based on the monomers chemical structure and thermal analyses. (C) 2008 Wiley Periodicals, Inc.